The present invention is related to a method of regulating pressure of an ink cartridge and the pressure regulating device thereof. In further detail, the present invention is directed to a pressure regulating device which makes use of a porous filter installed within a receiving chamber as a pressure regulating device to regulate the back pressure within the ink cartridge and the pressure regulating method using same.
Currently, the inkjet printer has become an indispensable printing peripheral device for a personal computer (or PC). With regard to the components of an inkjet printer, the ink cartridge is undoubtedly the most important expendable of the inkjet printer. With the intention of enabling the ink cartridge to reach an optimum condition and preventing the ink leakage in the middle of printing, the internal pressure-regulating mechanism must maintain a fine performance, such that the back pressure of the ink cartridge is able to be maintained at a stable level. Thereby a constant volume of ink can be supplied in operation. Otherwise, if the back pressure of the ink cartridge can not be maintained at a stable level, the ink is likely to leak from the print head or fails to be ejected out, and the longevity of the ink cartridge will be reduced accordingly.
U.S. Pat. No. 5,409,134 issued to Cowger et al. has addressed a superficial discussion to the back pressure issue, in which the xe2x80x9cback pressurexe2x80x9d mentioned herein indicates that a partial vacuum within the ink cartridge or the pressure that is slightly smaller than the external atmospheric pressure of the ink cartridge. The back pressure can permit the ink within the ink cartridge to be maintained at a stable state and inhibit the flow of the ink through the print head as the print head is inactive. Also, the back pressure can permit the ink to be ejected out smoothly as the print head is active. The bubble generator as disclosed in this example comprises an orifice extending from the recess in the bottom wall of the ink cartridge housing to communicate with the exterior, for introducing external air into the ink cartridge through the orifice to maintain the back pressure of the ink cartridge.
The pressure-regulating mechanisms for other ink cartridges are different with each other. An example of such a pressure-regulating mechanism is given in U.S. Pat. No. 4,931,811 issued to Cowger et al., also shown in FIG. 1 of the present invention. The pressure-regulating mechanism of FIG. 1 is basically formed by filling the ink cartridge with a porous material (foam sponge), which has a strong ink-absorbing capability to store ink, and matches up with the air vent 12 on the upside of the ink cartridge 11 to achieve the negative-pressure regulation function for the ink cartridge. Nonetheless, the pressure-regulating mechanism of FIG. 1 is disadvantageous because the porous material has a strong ink-absorbing capability, a certain amount of ink will be remained in the porous material when the ink within the cartridge is nearly used up, and it invisibly causes a waste of ink.
As depicted in FIG. 2, the negative pressure of the ink cartridge 21 is regulated by a negative-pressure regulating tube 20. The negative-pressure regulating tube 20 locally comprises air vents which uses capillary action to regulate the back pressure within the ink cartridge 21 and thus achieve the negative-pressure regulation function. Such pressure regulating mechanism also can be seen in U.S. Pat. No. 5,081,737 issued to Sato et al. The pressure regulating technique disclosed in this example is quite complicated, and the pressure regulating mechanism disclosed herein not only includes capillaries but also includes a greater number of components for allowing the air to permeate thin films.
FIGS. 3(a) and 3(b) show another embodiment of the pressure regulating mechanism using capillary action to regulate the pressure of the ink cartridge. The pressure regulating mechanism as shown in FIGS. 3(a) and 3(b) is also known by U.S. Pat. Nos. 5,600,358 and 5,526,030. The art of pressure regulating according to the pressure regulating mechanism of FIGS. 3(a) and 3(b) is to establish a conical opening 31 on the bottom of the ink cartridge 21. A number of ribs are provided on the opening 31 to hold the sphere 30, and crevices are created between the opening 31 and the sphere 30. The crevices then form capillary air vents. The sphere 30 is capable of containing the leaked ink by means of capillary action and keeping the moisture of the air vents.
As a part of prior art pertinent to the present invention, a co-pending U.S. patent application Ser. No. 09/433,235 filed on Nov. 4, 1999 by the Applicant describes an ink-jet cartridge, which includes a hollow tube including a first opening fixed on a cap of a housing and a second opening located at the bottom of the interior of the housing. This example is characteristic of the second opening having a smaller cross-section than the first opening. In this way, the pressure within the interior of the housing will be regulated by a capillary action of the ink contained in the second opening. However, this example fails to teach the way of using a receiving chamber installed with filtering material, such as porous material or fibrous material to regulate the pressure within the ink cartridge.
Another example relevant to the present invention may be seen from a co-pending U.S. patent application Ser. No. 09/867,196 filed on Jan. 9, 2001 by the Applicant, which is also incorporated herein for reference. This example describes a containing member connected to an opening of a hollow tube for containing therein an ink of the container, wherein the containing member is made of a material having a higher adherent wetting property than the hollow tube.
In conclusion, the pressure regulating techniques of FIG. 2 and FIG. 3 both utilize capillarity to regulate the negative pressure of the ink cartridge. When the internal pressure of the ink cartridge is dropped, air is supplemented to the ink cartridge through the capillaries to raise the pressure within the ink cartridge to a stable state. When the internal pressure of the ink cartridge is raised, the ink can flow out of the cartridge or into capillary orifices. However, when the internal pressure of the ink cartridge is dropped again, the pressure difference and the capillarity is able to inhale the ink back to the ink cartridge.
In view of the foregoing two types of pressure-regulating mechanism for the ink cartridge, though the manufacturing process of the first type pressure-regulating mechanism is simple, however, because the porous material occupies a large space, the ink content of the ink cartridge will be dropped. The second type pressure-regulating mechanism is quite complicated in structure, but it can fully utilize the space within the ink cartridge. Above all, both of the two types of pressure-regulating mechanism need high-precision process steps to match the curved members and conical columns with capillary orifices to form capillaries. In this way, the prior pressure-regulating mechanism will result in a complex assembling process, a low yield and a sumptuous cost.
In order to obviate the disadvantages of the prior press-regulating mechanism for ink cartridge, a pressure-regulating mechanism for ink cartridge with a simple structure and easy-to-manufacture characteristic is highly expected.
An object of the present invention is to provide a method of regulating pressure of an ink cartridge and the pressure regulating device thereof, in which a filter is telescoped by a sleeve and connected with one end of a conduit which has another end connected to the exterior of the ink cartridge. By way of the fiber being arranged with a uniform density, a capillary action is created on the filter to enable the filter to have the faculties to contain ink and supplement air through the conduit into the ink cartridge. The negative pressure within the ink cartridge then can be maintained at a best equilibrium state, and the ink cartridge is kept in a optimum ink supply status.
It is to be known from the above statements that the present invention is characterized by using a porous filter as the pressure-regulating component to simplify the sophisticated manufacturing process and the processing steps. The porous filter can be made up of bundles of fibrous material, and preferably the fibrous materials is made up of a polymer comprising polypropylene and polyethylene or the like, which has a density ranged from 0.01 g/cm3 to 0.8 g/cm3 and is selected based on the physical characteristic of ink absorption. If the filter is made up of fiber, it is axially arranged in order to prevent inadequate air supplement operation. More preferably, the filter comprises tens of bundles of fibrous material with a cross sectional diameter of 2.0 millimeter to 9.0 millimeter.
For the purpose of enabling the filter to connect with the conduit to create an overall capillary action, the filter is telescoped by a sleeve being telescoped with the conduit. Preferably, the sleeve is made up of an elastic material, such as rubber, silica gel and so forth. One embodiment of the sleeve comprises a hollow portion including a gradually-shrinking portion and a tubular portion. A perforation is established on the cross section of the gradually-shrinking portion for telescoping with the conduit. Another perforation is established on the cross section of the tubular portion for telescoping with the filter. The tubular portion is slightly longer than the filter so as to receive the entire filter. The filter is wrapped up by the sleeve so that the ink can flow into the filter unanimously. The two perforations of the sleeve is tightly cooperated with the members to be telescoped, such as conduit and filter, so that the conduit, sleeve and the filter are firmly jointed.
Now the foregoing and other features and advantages of the present invention will be more clearly understood through the following descriptions with reference to the accompanying drawings, in which: